Soft decision demodulation with bit erasure correction to reduce the effect of transmission errors in logarithmic PCM.

In this paper we analyze soft decision demodulation applied to mu-law Pulse Code Modulation (PCM). The PCM encoded waveforms are transmitted over Gaussian and Rayleigh fading channels by means of coherent phase shift keying modulation. Each bit in the PCM word is assigned its own erasure threshold. The erasure thresholds are optimized and are thus theoretically determined as a function of input power level to the quantizer, channel type and signal-to-noise ratio, and the relative mean square error power delta that occurs when a PCM word containing an erased bit is estimated by means of prediction or interpolation. In previous work this estimate was used to replace the PCM word with an erased bit. In this paper the estimate is used to decide the most likely value of the erased bit thus correcting most of the erasures without introducing errors in the replaced word.